Robert H. Grubbs (b. 27 February1942 in Possum Trot, Kentucky) is an American chemist and Nobel laureate.

As he noted in his official Nobel Prize autobiography, "In some places, my birthplace is listed as Calvert City and in others Possum Trot [NB: both in Marshall County]. I was actually born between the two, so either one really is correct." He spent his early childhood in Marshall County and attended public school at McKinley Elementary, Franklin Junior High and Paducah Tilghman High School in Paducah, Kentucky. Grubbs studied chemistry at the University of Florida (B.S. and M.S.), where he worked with Merle Battiste, and Columbia University, where he obtained his Ph.D. under Ronald Breslow in 1968.

He next spent a year with James Collman at Stanford University. He was then appointed to the faculty of Michigan State University. In 1978 he moved to California Institute of Technology where he is presently Victor and Elizabeth Atkins Professor of Chemistry.

His main interests in organometallic chemistry and synthetic chemistry are catalysts, notably Grubbs' catalyst for olefin metathesis and ring-opening metathesis polymerization with cyclic olefins such as norbornene. He also contributed to the development of so-called "living polymerization".

Grubbs's many awards have included: Alfred P. Sloan Fellow (1974-76), Camille and Henry Dreyfus Teacher-Scholar Award (1975-78), Alexander von Humboldt Fellowship (1975), ACS Benjamin Franklin Medal in Chemistry (2000), ACS Herman F. Mark Polymer Chemistry Award (2000), ACS Herbert C. Brown Award for Creative Research in Synthetic Methods (2001) and the Nobel Prize in Chemistry (2005). He was elected to the National Academy of Sciences in 1989 and a fellowship in the American Academy of Arts and Sciences in 1994.

Grubbs received the 2005 Nobel Prize in Chemistry, along with Richard R. Schrock and Yves Chauvin, for his work in the field of olefin metathesis.